Woocommerce – wc_add_notice() not adding to session when nothing in the cart

Solution:

Ok so I figured it out! It appears that woocommerce 2.1 > does not set a cookie at until the cart is used, to help with caching or something. Here is a thread on it : https://github.com/woothemes/woocommerce/issues/4920

Solution for me was to add this to my function :

do_action( 'woocommerce_set_cart_cookies',  true );

Hope this helps someone else.